The proposal is directed at achieving a fuller understanding of the following aspects of liver glycogen. The question whether glycogen is a proteoglycan will be examined in detail. Recent work suggests that the carbohydrate macromolecule originates by growth on a protein primer. Native glycogen will be characterized in terms of its content of protein and the nature of the covalent attachment to protein. The protein will be characterized and the enzyme system responsible for creating the carbohydrate-protein linkage will be examined. A study will be made of the possibility that glycogen is laid down on the smooth endoplasmic reticulum of the liver by a complex of enzymes associated with this organelle. The question of the existence of protein-bound and protein-free species of glycogen in liver will be re-examined. The turnover of liver glycogen will be studied in perfused liver and hepatocyte. Glycogen will be synthesized in vitro and its structure compared with native glycogen. This will require the purification and characterization of the branching enzyme and the debranching enzyme system. The kinases involved in the phosphorylation of glycogen synthase, phosphorylase kinase and phosphorylase will be isolated and characterized. Further evidence will be sought for coordinate control of enzymic activity via a single protein phosphatase acting on multiple substrates. Multisite phosphorylation of phosphorylase kinase and glycogen synthase, a possible additional regulatory mechanism, will be studied.